(a) Field of Disclosure
Embodiments of the inventive concept relate to a thin film transistor, a thin film transistor array panel, and a manufacturing method of a thin film transistor, and in detail, relates to a thin film transistor including an oxide semiconductor and a manufacturing method of a thin film transistor.
(b) Description of Related Technology
Electric elements such as resistors, capacitors, diodes, and thin film transistors (TFT) are used in various fields. Among these, the thin film transistors (TFT) in particular is often used for defining switching and driving elements in a flat panel display apparatus such as a liquid crystal display (LCD), an organic light emitting device (organic light emitting diode (OLED) display), and an electrophoretic display. Within the structure of the TFT, the semiconductive portion thereof is an important part for determining behavior characteristics of the TFT. Currently, silicon (Si) is widely used as the semiconductor in the TFT and other electric elements that need a semiconductive portion. The utilized silicon may be an amorphous silicon type or a polysilicon type or a monocrystalline type depending on the crystallization micro-structure of the semiconductive material. Monocrystalline silicon tends to be the most difficult to mass produce whereas the amorphous silicon type has a comparatively simpler manufacturing process. However, the amorphous silicon type has a comparatively and undesirably low, charge-carrier mobility such that there is a limit to using it for manufacturing a high performance (e.g., high switching speed) thin film transistor. Between the relatively poor performance of the amorphous silicon type and the relatively superior performance of the monocrystalline silicon type, there is the polysilicon type which has higher charge-carrier mobility than that of amorphous silicon. However, the process of crystallizing amorphous silicon to form polysilicon requires a great deal of time, energy and manufacturing cost. Also, because the crystallizing step increases process complexity, the possibility of defects during mass production that employs such a crystallizing step may increase. Thus, semiconductive oxides which use a metal oxide having semiconductive properties are coming into favor because it does not require the process of crystallization to get the higher charge-carrier mobility. Semiconductive oxides require a lower cost and higher uniformity as compared with polycrystalline silicon as well as higher charge-carrier mobility and a relatively high ON/OFF ratio as compared with amorphous silicon. The electrical characteristics of thin film transistors of the semiconductive oxide type may be greatly affected by the micro-structure and uniformity of the semiconductive oxide material, where the latter may be affected by the process used to make the semiconductive oxide material. Accordingly, research on the micro-structure and the process of forming thin film transistors using the semiconductive oxide material has been ongoing. It is to be understood that this background of the technology section is intended to provide useful background for understanding the here disclosed technology and as such, the technology background section may include ideas, concepts or recognitions that were not part of what was known or appreciated by those skilled in the pertinent art prior to corresponding invention dates of subject matter disclosed herein.